Countershaft transmissions are widely used in the drives lines of vehicles such as wheel loaders, earthmoving tractors, and other off-highway vehicles because the plurality of rotating clutch assemblies and associated gears can be so positioned on the usual parallel shafts as to allow considerable flexibility in adapting them to different space requirements and to different drop heights between the input and output axes. Moreover, a substantial number of simple parts and/or similarly sized parts can be used for manufacturing economy. Exemplifying the art in this area are the following U.S. Pat. Nos.: 3,080,767 issued Mar. 12, 1963 to S. J. Price, Jr.; 3,425,293 issued Feb. 4, 1969 to H. S. Krawczyk, et al; 3,465,609 issued Sept. 9, 1969 to J. F. Fisher, et al; 3,858,455 issued Jan. 7, 1975 to R. L. Sisson, et al; 3,913,616 issued Oct. 21, 1975 to J. Horsch; and 4,341,127 issued July 27, 1982 to E. Stodt.
While such countershaft transmissions have a considerable number of advantages, they are deficient in several other respects. One problem is that if the input member of several of these transmissions is connected to the engine and/or optional hydrodynamic torque converter excessive space is required above the axis of the input shaft. Specifically, it would be necessary in several vehicular applications to raise the floor plates and elevate the entire operator station in order to obtain sufficient clearance above the input shaft's axis to accommodate large diameter components such as a rotating clutch thereat.
In addition, the countershaft transmission should provide an auxiliary drive means for driving two or more hydraulic pumps in relatively nested locations so as to not unduly extend the overall dimensions of the transmission. These pumps should be continuously and positively driven as a function of the speed of the input shaft of the countershaft transmission and not be affected by any gear change of the transmission. Moreover, the auxiliary drive means should also be able to provide a power take off (PTO) operation as a function of the input shaft speed without interference with the operation of the pumps.